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Open AccessArticle

Terrain Feature Estimation Method for a Lower Limb Exoskeleton Using Kinematic Analysis and Center of Pressure

1
Motion Control Laboratory, Department of Mechanical Engineering, Yonsei University, Seoul 03722, Korea
2
Construction Robot and Automation Laboratory, Department of Civil & Environmental Engineering, Yonsei University, Seoul 03722, Korea
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(20), 4418; https://doi.org/10.3390/s19204418 (registering DOI)
Received: 19 July 2019 / Revised: 2 October 2019 / Accepted: 10 October 2019 / Published: 12 October 2019
(This article belongs to the Special Issue Sensors and Wearable Assistive Devices)
While controlling a lower limb exoskeleton providing walking assistance to wearers, the walking terrain is an important factor that should be considered for meeting performance and safety requirements. Therefore, we developed a method to estimate the slope and elevation using the contact points between the limb exoskeleton and ground. We used the center of pressure as a contact point on the ground and calculated the location of the contact points on the walking terrain based on kinematic analysis of the exoskeleton. Then, a set of contact points collected from each step during walking was modeled as the plane that represents the surface of the walking terrain through the least-square method. Finally, by comparing the normal vectors of the modeled planes for each step, features of the walking terrain were estimated. We analyzed the estimation accuracy of the proposed method through experiments on level ground, stairs, and a ramp. Classification using the estimated features showed recognition accuracy higher than 95% for all experimental motions. The proposed method approximately analyzed the movement of the exoskeleton on various terrains even though no prior information on the walking terrain was provided. The method can enable exoskeleton systems to actively assist walking in various environments. View Full-Text
Keywords: walking terrain; terrain estimation; terrain classification; kinematic analysis; center of pressure; lower limb exoskeleton walking terrain; terrain estimation; terrain classification; kinematic analysis; center of pressure; lower limb exoskeleton
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Shim, M.; Han, J.I.; Choi, H.S.; Ha, S.M.; Kim, J.-H.; Baek, Y.S. Terrain Feature Estimation Method for a Lower Limb Exoskeleton Using Kinematic Analysis and Center of Pressure. Sensors 2019, 19, 4418.

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  • Externally hosted supplementary file 1
    Doi: 10.5281/zenodo.3343073
    Link: https://zenodo.org/record/3343073#.XTIGfvIzZUQ
    Description: Video S1: Kinematic analysis results of the exoskeleton for level walk, stair ascent, stair descent, ramp ascent, and ramp descent; Video S2: Kinematic analysis result for the motion of the exoskeleton in a building environment.
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